The present invention relates to an electronic component unit which an electronic component is mounted on a substrate, and an electronic assembly using the electronic component unit, as well as a method for manufacturing the electronic component unit.
In manufacturing an electronic component unit of the present category under discussion, a substrate is tested, before it is mounted with electronic component, with respect to conduction of electrical conductive patterns formed on the substrate. Only the substrates which passed the conduction test are sent to a subsequent process step to be mounted with electronic component.
However, some of the electronic component units are often rejected due to poor connection at the final inspection, despite the fact that such units are made with substrates approved at the above conduction test. It has been found out that the rejection is caused by the phenomena described in the following. The conductivity test of a substrate is made by contacting a piece of electroconductive rubber on the surface of connecting area of the conductive pattern. A part of the electroconductive rubber inevitably remains on the connecting area after the test. Although the electroconductive rubber as a whole has a good electrical conductivity, the remaining particle staying on the connecting area has a poor electroconductivity, or almost non-electroconductive. As a result, when an electrode of electronic component is attached on the connecting surface, the electrical connection may be deteriorated by the remaining particle staying between the surfaces. Further, in some cases, conduction troubles are brought about by an insufficient strength of connection between substrate and electronic component.
The present invention addresses the prevention of rejection due to poor electrical connection.
An invented electronic component unit comprises a substrate having a conductive pattern on at least one of the surfaces, and an electronic component mounted on the surface of the substrate, on which surface the conductive pattern has been formed; in which, the electronic component is disposed with its electrode facing to the substrate, the connecting area of the conductive pattern facing the electrode is roughened, and the electrode of electronic component is connected to the roughened surface of connecting area by means of an electroconductive adhesive.
An invented electronic assembly is structured with an electronic component unit of the present invention mounted on another substrate.
An invented method for manufacturing an electronic component unit comprises the steps of forming a conductive pattern on at least one of the surfaces of a substrate, roughening at least connecting area of the conductive pattern, and connecting the roughened surface of connecting area and electrode of electronic component by means of electroconductive adhesive.
According to the present invention, the electrical connection between electrode of electronic component and the surface of connecting area is brought to a stable state because, as a result of the roughening operation applied on the connecting area of conductive pattern, the particle of poor conductive material sticking on the surface of connecting area is removed, at the same time the surface area of connecting area is increased. Also, the roughening of the surface increases an anchoring effect of electroconductive adhesive to an enhanced mechanical connection between electrode of electronic component and connecting area of conductive pattern.